Biotechnology and Pharmaceutical Investor Research
Phase III Trials

Phase III (or Phase 3) clinical trials involve giving relatively large numbers of humans drugs to see if they are effective and safe. The large number of subjects makes it easier to prove that a therapy causes statistically significant improvement in patients. It also allows for rarer side effects to be detected than in a Phase II study. Typically 1000 to 3000 patients are included in the studies.

Phase III trials usually involve a control group that receive placebos. Preferably they are double-blind (neither the patients nor the researchers know who gets the placebos and who gets the real drug).

The FDA and the researchers agree in advance on what achieved endpoints will be a success for the trial.

For investors the Phase III results are the only results that matter. Phase II trials may indicate that a drug is likely to do well in Phase III, but only achieving the goals of Phase III trials allows the company to submit the drug for marketing approval to the FDA (called filing an NDA).

Phase III trials can also be used for label expansion. Having been successful for one disease (often a very specific subtype of what a layperson would consider a disease), a separate Phase III trial may be tried on another disease, usually one closely related to the prior success. It may even be for the exact same disease at a different stage of progress, or in combination with a different drug or therapy.

An important outcome of Phase III trials is support for the exact label. A label, for example, may warn against certain types of patients being treated with a drug, or may recommend that certain types of patients be closely monitored if they are given the drug.